Reinvent I2C ops

Do not use the global platform_i2c_transfer() function that can only be
implemented by a single driver. Instead, make a `struct device` aware
transfer() function the only interface function for I2C controller dri-
vers to implement.

To not force the slave device drivers to be implemented either above
generic I2C or specialized SMBus operations, we support SMBus control-
lers in the slave device interface too.

We start with four simple slave functions: i2c_readb(), i2c_writeb(),
i2c_readb_at() and i2c_writeb_at(). They are all compatible to respec-
tive SMBus functions. But we keep aliases because it would be weird to
force e.g. an I2C EEPROM driver to call smbus_read_byte().

Change-Id: I98386f91bf4799ba3df84ec8bc0f64edd4142818
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/20846
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/device/i2c_bus.c

@@ -0,0 +1,161 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <console/console.h>
+#include <device/smbus.h>
+#include <device/i2c_bus.h>
+
+struct bus *i2c_link(struct device *const dev)
+{
+	if (!dev || !dev->bus)
+		return NULL;
+
+	struct bus *link = dev->bus;
+	while (link) {
+		struct device *const parent = link->dev;
+
+		if (parent && parent->ops &&
+		    (parent->ops->ops_i2c_bus || parent->ops->ops_smbus_bus))
+			break;
+
+		if (parent && parent->bus)
+			link = parent->bus;
+		else
+			link = NULL;
+	}
+
+	if (!link) {
+		printk(BIOS_ALERT, "%s Cannot find I2C or SMBus bus operations",
+		       dev_path(dev));
+	}
+
+	return link;
+}
+
+int i2c_readb(struct device *const dev)
+{
+	struct device *const busdev = i2c_busdev(dev);
+	if (!busdev)
+		return -1;
+
+	if (busdev->ops->ops_i2c_bus) {
+		uint8_t val;
+		const struct i2c_msg msg = {
+			.flags	= I2C_M_RD,
+			.slave	= dev->path.i2c.device,
+			.buf	= &val,
+			.len	= sizeof(val),
+		};
+
+		const int ret = busdev->ops->ops_i2c_bus->
+			transfer(busdev, &msg, 1);
+		if (ret)
+			return ret;
+		else
+			return val;
+	} else if (busdev->ops->ops_smbus_bus->recv_byte) {
+		return busdev->ops->ops_smbus_bus->recv_byte(dev);
+	} else {
+		printk(BIOS_ERR, "%s Missing ops_smbus_bus->recv_byte",
+		       dev_path(busdev));
+		return -1;
+	}
+}
+
+int i2c_writeb(struct device *const dev, uint8_t val)
+{
+	struct device *const busdev = i2c_busdev(dev);
+	if (!busdev)
+		return -1;
+
+	if (busdev->ops->ops_i2c_bus) {
+		const struct i2c_msg msg = {
+			.flags	= 0,
+			.slave	= dev->path.i2c.device,
+			.buf	= &val,
+			.len	= sizeof(val),
+		};
+		return busdev->ops->ops_i2c_bus->transfer(busdev, &msg, 1);
+	} else if (busdev->ops->ops_smbus_bus->send_byte) {
+		return busdev->ops->ops_smbus_bus->send_byte(dev, val);
+	} else {
+		printk(BIOS_ERR, "%s Missing ops_smbus_bus->send_byte",
+		       dev_path(busdev));
+		return -1;
+	}
+}
+
+int i2c_readb_at(struct device *const dev, uint8_t off)
+{
+	struct device *const busdev = i2c_busdev(dev);
+	if (!busdev)
+		return -1;
+
+	if (busdev->ops->ops_i2c_bus) {
+		uint8_t val;
+		const struct i2c_msg msg[] = {
+			{
+				.flags	= 0,
+				.slave	= dev->path.i2c.device,
+				.buf	= &off,
+				.len	= sizeof(off),
+			},
+			{
+				.flags	= I2C_M_RD,
+				.slave	= dev->path.i2c.device,
+				.buf	= &val,
+				.len	= sizeof(val),
+			},
+		};
+
+		const int ret = busdev->ops->ops_i2c_bus->
+			transfer(busdev, msg, ARRAY_SIZE(msg));
+		if (ret)
+			return ret;
+		else
+			return val;
+	} else if (busdev->ops->ops_smbus_bus->read_byte) {
+		return busdev->ops->ops_smbus_bus->read_byte(dev, off);
+	} else {
+		printk(BIOS_ERR, "%s Missing ops_smbus_bus->read_byte",
+		       dev_path(busdev));
+		return -1;
+	}
+}
+
+int i2c_writeb_at(struct device *const dev,
+		  const uint8_t off, const uint8_t val)
+{
+	struct device *const busdev = i2c_busdev(dev);
+	if (!busdev)
+		return -1;
+
+	if (busdev->ops->ops_i2c_bus) {
+		uint8_t buf[] = { off, val };
+		const struct i2c_msg msg = {
+			.flags	= 0,
+			.slave	= dev->path.i2c.device,
+			.buf	= buf,
+			.len	= sizeof(buf),
+		};
+		return busdev->ops->ops_i2c_bus->transfer(busdev, &msg, 1);
+	} else if (busdev->ops->ops_smbus_bus->write_byte) {
+		return busdev->ops->ops_smbus_bus->write_byte(dev, off, val);
+	} else {
+		printk(BIOS_ERR, "%s Missing ops_smbus_bus->write_byte",
+		       dev_path(busdev));
+		return -1;
+	}
+}